schultz10e_ch13.ppt

Schultz & Schultz 10e 1
Copyright © 2010 Pearson Education, Inc.,
Upper Saddle River, NJ 07458. All rights reserved
Psychology and Work Today
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Learning Objectives
After reading this chapter, students should be able to:
• Define ergonomics and describe its role and function in the
workplace
• Outline the history and scope of engineering psychology
• Explain the relationship of displays, controls, and the human
operator in a person-machine system
• Describe the major considerations involved in the design of a
workspace
• Contrast the advantages and disadvantages of auditory and visual
presentation of information
• Define telematics and its importance to engineering psychology
• Describe the use of human factors in everyday life, with examples
• Understand and explain the factors that should be considered in
the design of a computer work station
• Understand the role and impact of robots in the workplace

Engineering Psychology
• The design of machines and equipment for
human use, and the determination of the
appropriate human behaviors for the efficient
operation of the machines
• (interaction between machine & human and make it perform better)
• Also called
• Human factors
• Human engineering
• Ergonomics

History and Development
• Prior to 1940, engineers made machines without
considering the human factor
• The worker was adapted to the machine through
time-and-motion studies
• WW II weaponry was complex but did not perform
up to expectations, thus giving rise to engineering
psychology
• Example: There was no consistency in design of aircraft
controls. “On” position for some controls was up, for
others, down – difficult to remember in a dog fight. Many
pilots died as a result

Time and Motion Study
• An early attempt to redesign work tools and to
reshape the way workers performed routine,
repetitive jobs
• F.W. Taylor (1898), of scientific management
fame, performed first empirical demonstration of
the relationship between work tools and worker
efficiency
• Introduced shovels of different sizes for handling different
materials
• 21 1/2 pounds was the most efficient load at a U.S. Steel company
study
• Saved the company $78,000 per year

Time and Motion Study
• Frank and Lillian Gilbreth were interested in the
mechanics of job performance to eliminate
unnecessary motion
• Started with improving the efficiency of bricklaying
• Increased rate of bricklaying from 120 to 350 bricks an
hour by reducing motions from 18 to 5
• The basic unit of motion was the Therblig
(Gilbreth spelled backwards)
• Gilbreths had 12 children – their lives were
depicted in the book/movie Cheaper by the
Dozen
• More info at
http://gilbrethnetwork.tripod.com/front.html

Efficiency Rules for Manual Jobs
• Minimize reaching distance from worker
• Symmetrical movements of both hands(e.g. no
need to step by step, but togther)
• Hands should never be idle except during
breaks
• Hands never do tasks that can be performed
by other parts of body
• Work materials held by a vice when possible
• Workbench height sufficient to stand or sit on
high stool – alternating reduces fatigue

Person-Machine System
• A system in which human and mechanical components
operate together to accomplish a task
• Human operator receives input on machine status from the
displays(e.g. speedometer)
• Such systems vary in the extent to which the human
operator is actively and continuously involved
• Humans remain important components of automated
manufacturing systems
• Automation makes the engineering psychologist’s job more
demanding as monitoring machinery is more monotonous
than actually operating it

Allocating Functions
• Engineers first carefully analyze each
process in the functioning of the total system
to determine its characteristics
• Speed, accuracy and frequency with which it is
performed
• Stress under which it occurs
• They then make decisions regarding person
- machine division of labor based on relative
strengths and weaknesses of each

Machine Strengths
• Detecting stimuli beyond human sensory
capacities (e.g. high precision parts)
• Monitoring reliably for lengthy periods(sometimes
not only consider the cost, but also the quality are stable)
• Making large numbers of rapid, accurate
calculations
• Storing and retrieving vast amounts of
information
• Applying continuous and rapid physical force
• Engaging in repetitive activities

Machine Limitations
• Not very flexible
• Cannot learn from errors (some AI machine can do it now)
• Cannot improvise (sometime can’t something new)
• When operators only monitor, disastrous
results can happen (may create danger)
• e.g., bored pilots or subway drivers
• However, full automation is dangerous as
systems can fail – no intervention available
without human monitor

Principles for Workspace Design
1. All materials should be placed in order in
which they will be used so paths of
movements will be continuous
2. Tools should be pre-positioned for use
3. All parts and tools should be within
comfortable reach
• Greater than about 28 inches causes
unnecessary repositioning and consequent
loss of efficiency and increased fatigue

Other Design Considerations
• Heights of all working surfaces should be
adjustable (research shows that nearly 20% don’t vary the
height even the table and chair are adaptable)
• Hand tools should be designed for use
without bending wrists
• Hammers with angled handles work better
• Properly designed tools affect productivity,
satisfaction, and physical health
• e.g., reduction of carpal tunnel syndrome

Ergonomic Pliers

Visual Displays
• Visual presentation is most appropriate when
• Message is long, difficult and abstract
• Environment is too noisy for auditory signals
• Auditory channels are overloaded
• Multiple kinds of information to be presented
simultaneously

Auditory Information
• Auditory(Can be heard) presentation most effective
when:
• Information is short, simple, and straightforward
• Message is urgent
• Environment is too dark for visuals
• The operator’s job requires moving to different
locations

Quantitative Visual Displays
• Quantitative displays present a precise
numerical value such as speed, altitude or
temperature
• An open window display is read with fewest errors,
and the vertical display was misread one third of
the time (See Fig. 13-5)
• Digital display can be read faster with fewer errors,
but cannot be used in all situations
• e.g., if conditions are rapidly changing, or need to
know direction of change

Qualitative Visual Displays
• Qualitative displays present a range
rather than a precise numerical value
• e.g., red area hot – green area normal – yellow
area cold
• Consistent patterning makes multiple
displays easier to read
• Used in aircraft cockpits
• Unpatterned displays force operator to
read each dial separately

Check Reading Visual Displays
• Check reading displays (yes or no system)
sometimes referred to as go/no go
• Tells operator whether the system is:
• On or off
• Safe or unsafe
• Normal or abnormal
• Warning light most common
• Twice as bright as background
• Centered in field of vision
• Flashing

Auditory Displays
• Auditory displays can be more compelling than
visual because
• Ears always open
• Multi-directional
• Visual often taxed to capacity
• Problem with “nuisance alarms”
• If alarms are too sensitive or occur too frequently,
they are often ignored
• At Canadian nuclear power plant, >50% of alarms did
not provide useful information

Tactile Displays
• Tactile communication is through the skin
senses (e.g., Braille) – feel the message
• Research has been conducted for 50 years,
but interest in the topic lagged
• New tactile devices now being developed
• Vibrating vest that writes messages on wearer’s
back can be used where visual or auditory
communication is not available or advisable (e.g.,
on battlefield)

Guidelines For Controls
• Control-body matching
• Most rely on hands and feet
• No one limb should be given too many tasks
• Hands more precise
• Feet exert more force
• Control-task compatibility
• A control action should imitate the movements it
produces
• Turning steering wheel right makes right turn
• When possible, combining controls that perform
similar or related functions is more efficient

Guidelines For Controls
• Identification of controls
• Controls should be clearly marked or coded
• e.g., shape coding (different shape may have different
function)for touch recognition
• Placement of controls
• Consistency and uniformity is important
• Consider cultural influences on preferences
• Emergency controls in line of sight, clearly
distinguishable and protected with a cover
• Group related controls and displays according to
function

Human Factors in Everyday Life
• Human factors no longer confined to tanks,
airplanes and work areas
• Telematics deals with wireless information
technology such as GPS, Satellite radio, and
automatic collision notification systems
• Examines cell phone use while driving to minimize
distractions and prevent accidents
• 4 times likelier to be in a crash when on cell phone
• Use of auditory signals to alert drivers they are too
close to another car, or warn pilots of collision
• Sharpened ice cream scoops and ergonomic
spatulas to reduce carpal tunnel….

Key Terms
• Auditory displays
• Check reading visual displays
• Engineering psychology
• Person-machine systems
• Qualitative visual displays
• Quantitative visual displays
• Shape coding
• Time-and-motion study

1. A
2. B
3. B
4. C
5. C
6. D
7. A
8. C
9. A
10. A
11. A
12. d
1. A
2. D
3. B
4. B
5. C
6. D
7. B
8. C
9. C
10.C
11.A
12.D

schultz10e_ch13.ppt

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